Qualitative and quantitative detection of isothiocyanates; quantification of erucin and phenethyl isothiocyanate in Kohlrabi by a reverse phase HPLC-DAD method.

Abstract

Several breakdown products, including isothiocyanates (ITCs) are formed by hydrolysis of naturally occurring secondary metabolites in Brassica plants. These compounds are known to exert positive effects on health. The present study aimed to detect the presence of these volatile compounds in the raw and fermented Kohlrabi and optimise and validate a HPLC-DAD method for quantification of erucin and phenethyl isothiocyanate in Kohlrabi. Correlation coefficients of 0.979 and 0.978 were attained over the range 1-20 μg/ml and 0.5-10 mg/ml for erucin and phenethyl isothiocyanate, respectively, The LOD and LOQ values for erucin and phenethyl isothiocyanate were 3.36, 10.18 μg/ml and 1.73, 5.26 mg/ml, respectively. The accuracy for the analysis was confirmed by the recovery values of 97-98%. The validated method was used to analyse these two compounds in raw and fermented Kohlrabi. Furthermore, the total glucosinolate and total isothiocyanate content of raw and fermented extracts of Kohlrabi were also evaluated.